Ever the pragmatist, mezzo Carmel Carroll says the main appeal of the director's chair was the chance to give directions rather than taking those of others.

"Back in the days of Mercury Opera, I'd wanted to change the things that I saw other people do," she says. "Quite often I would have an idea that I would like to see happen and I'd get frustrated when I couldn't try it out."

The opportunity came 14 years ago with an intimate production of Menotti's The Medium at James Wallace's Rannoch.

"When Helen Medlyn and Stephen De Pledge didn't have a director, I put my hand up and said, 'Let me! Let me!"' she says.

It was an impressive debut and now, after years of undertaking productions all over the country, Carroll directs Opera Factory's upcoming The Turn of the Screw.

Benjamin Britten's 1954 operatic take on the Henry James novel is a shivery piece. One of the challenges, Carroll says, is "having two sets of characters, the humans and the ghosts, and to be able to make the ghosts different without 65 special lighting effects and all the other weird and wonderful things you could do on a big budget".

Nevertheless, she is "not interested in blood and gore or people wearing lots of make-up. It's a quiet fear we're dealing with here."

The Turn of the Screw presents a mystery on more than one level. Perhaps, some suggest, the whole plot is a figment of the protagonist's imagination.

Carroll finds it an interesting proposal to discuss with her cast.

"It sows the seeds of confusion, and confusion is the friend of mystery and ghost stories. The idea that this story might not be true adds to the feeling of unease," Carroll says.

She stresses the significance of the title in terms of its musical setting. "The Turn of the Screw implies something getting more and more bound up and tighter, and that's what happens in the music."

Britten's score, laid out in a series of carefully worked out variations, presents coup after coup. One, says Carroll, comes "when the children are singing Lavender's Blue while the governess and housekeeper are talking about how beautiful the children are.

"Some of the most beautiful sounds come from the ghost character of Quint, especially in his farewell to the boy Miles near the end of the opera."

Carroll has her own thumbnail sketches for the characters, which are brought to life by a cast that includes Emma Sloman as the governess, Mary Newman-Pound as the housekeeper, Mrs Grose, Cameron Barclay as Quint, Rachel Day as Miss Jessel and Tizane McEvoy as Flora.

The governess is "all heart and not quite enough discernment", Quint is "not evil but just selfish" and Miss Jessel is "the archetypal victim, a weak fool who blames everyone else".

The role of the young Miles, played by actor David Hemmings in the opera's 1954 production, is shared by boy sopranos Thomas White and Conrad Edwards.

For Carroll, Miles is "not a troubled child, just a boy with his feet on the wrong path".

The Turn of the Screw promises as gripping a night in the theatre as one could wish for.

"People need to get away from screens and electricity and all the stuff that you don't have to be human to operate," says Carroll.

"I would like to think that something inside of them can be awakened, stimulated and energised by experiencing this music."